Carburetor



y Z0, 1947- R. w. SUTTON ETAL 2,420,917

' CARBURETOR Filed 001;. s, 1941 2 Sheets-Sheet 1 IIIIIIIIIIIIII/t INVENTORS 208E197 W. SUTTON BY ALBEQT h. W/NKLEE a e %Z'ORNEY% ay 20, 1947. Rfw. SUTTON ET AL 2,429,917

CARBURETOR Filed Oct. z 1941 2 Sheet-Sheet 2 INVENTORS EOBEETW. surro/v.

BY ALBERT h, W/NKLEE g AiTORNEY Patented May 20, 1947 UNITED STATES CARBURETOR Robert W. Sutton and Albert H. Winkler, South Bend, Ind., assigno'rs to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application October 3, 1941, Serial No. 413,432

3 Claims.

This invention relates to carburetors for internal combustion engines and more particularly to means for automatically controlling the carburetor choke valve to vary the air to fuel ratio of the mixture in accordance with the requirements of the engine under various operating conditions.

Internal combustion engines generally require an extremely rich mixture for cold starting and a moderately rich mixture during the warm-up period of engine operation, said latter mixture being substantially leaner than the former and somewhat richer than that needed by the engine at normal operating temperatures.

The usual method of producing a rich mixture in a carburetor for starting when the engine is cold is to close the choke valve so as to restrict the flow of air into the carburetor, thus producing a suction at the fuel nozzle which will draw abnormal quantities of gasoline into the air stream.

Various means have been proposed for automatically controlling the choke valve so as to close it for starting, effecting a sudden partial opening thereof as the engine begins firing, and then gradually moving the valve to the fully open position in order to lean out or grade down the mixture to meet the requirements of the engine during the warm-up period and for normal operation.

Generally in carburetors having an automatic choke valve control, the valve is of a type actuated by air pressure such as an offset butterfly valve; and the most commonly employed automatic choke mechanism for controlling the valve includes a thermostat and a suction responsive device. The thermostat is adapted to hold the valve in closed position when the temperature is low and to gradually open said valve or permit same to open as the temperature rises. The suction device, which includes a piston operable within a cylinder, is responsive to manifold vacuum posterior to the carburetor throttle and is adapted to modify the action of the thermostat as soon as the engine begins to operate under its own power.

However, the piston arrangement of suction responsive devices of this character are unsatisfactory in that they must be very sensitive and, even very fine particles of foreign matter, such as sand or dust may impair the free movements of said piston or may even cause the piston to stick which, if the choke valve is only partially open, will result in an excessive quantity of fuel in the mixture which in turn will result in excessive fuel consumption and improper operation of the engine, overloading and the like. If the piston sticks in a manner to prevent closing of the choke valve it will [be impossible to start the enginewhen cold.

$uch devices are also objectionable because the suction available in the manifold varies widely and does not always provide the proper modification of the action of the thermostat to correspond with the requirements of the engine.

5 Another disadvantage of the vacuum piston device in automatic choke control mechanisms is that the vacuum passages of said device may become impeded or clogged with dust or other foreign matter or may leak, thereby causing faulty and improper functioning and under some circumstances may render the device inoperative.

The present invention is intended to eliminate the vacuum piston device in an automatic choke control mechanism of the aforementioned character and thereby eliminate the disadvantages thereof, While at the same time providing accurate and dependable automatic control of the choke valve whereby to supply the proper air to fuel ratio, variable in accordance with the requirements of the engine for cold starting, during the warming-up period, and for normal engine operation.

Another object of the invention is to provide a device of this character that will limit opening of the pressure actuated choke valve while the engine is being cranked.

It is still another object of the present invention to provide a device for automatically controlling the choke valve whereby said choke valve may be positively held in an open position during the warming-up period of engine operation when the engine suction may be too low to open the valve against the force of the thermostat.

A further object of the invention is to provide a device of this character wherein said positive latching of the choke valve in a suitable partly open position is effective throughout at least the lower throttle range and during at least the initial portion of the warming-up period of engine operation.

A further object of the invention is to provide a device of this character which will positively render the latching means operative after the engine has been started.

A still further object of the invention is to provide a mechanism of this character which will render the latching means inoperative while the engine is being started.

Other objects of the invention are to provide a device of this character that has relatively few parts, that is simple and positive in construction and operation and not likely to become inoperative from sticking parts or the like, and that is relatively inexpensive to manufacture.

Still other objects and advantages of the invention will be apparent to those skilled in the art from the following description or may be ascer tained from a study of the accompanying drawings which illustrate ,a preferred embodiment of the invention. It will be evident that the principles of th invention may be incorporated in various forms and the employment of any structures, arrangements, or modes of operation that are properly within the scope of the appended claims is contemplated.

Figure 1 is an elevational view of a carburetor embodying the present invention and showing the relative position of the parts when the carburetor has cooled after normal operation of the engine;

Figure 2 is a partial elevational view of the same showing the position of the respective parts when the throttle lever is moved to a part open position, to permit the choke valve to be closed by the cold thermostat;

Figure 3 is a fragmentary view showing the throttle lever and associated parts with said lever in the closed fast idle position for cranking the engine;

Figure 4 is a view similar to Figure 2 showing the relative position of the respective parts during the initial portion of the warming up period of engine operation and with the throttle valve closed to the fast idle position;

Figure 5 is a similar view showing the position of the parts during normal idling operation of the engine when warm; and

Figure 6 is an isometric view of the throttle lever and associated parts showing their relative arrangement.

Throughout the specification reference to the position of various parts or the direction of movement thereof are made with regard to the device as viewed in the drawings.

Referring more particularly to the drawings, there is illustrated a carburetor l attached to the intake manifold I l of an internal combustion engine and having an air pressur operated air or choke valve l2 and a throttle l4. Carburetor I0 is shown as a plain tube downdraft carburetor, this type being shown by way of example only as the invention may be applied to any preferred type such as an updraft or horizontal delivery carburetor, or the like.

The chOke valve I2 is ofiset and secured to a shaft journalled in the walls of the air inlet passage l8 of the carburetor. A coiled bimetallic thermostat 20 is attached to one end of shaft l6 and adapted to normally close the choke valve I2 when said thermostat is cold and to govern the degree of opening of said valve 12 in accordance with well-known practice. If desired, a heat casing 2| may be provided about the thermostat and connected with a stove 23 on exhaust manifold E by means of a conduit C thereby efiecting more rapid heating of the thermostat as the engine warms up.

The throttle I4 is mounted on a throttle shaft 22 journalled in the walls of mixture outlet passage 24 of the carburetor. One end of the shaft 22 extends through a bearing 25 fixed in a boss 26 formed integral with the walls of the mixture passage 24 and a throttle lever 28 is attached to said end of shaft 22, said lever being connected by a rod 30 to the usual accelerator pedal (not shown). A return spring, shown diagrammatically at 32, is attached to rod 30 for yieldingly urging the lever 28 in a direction to normally close the throttle l4. The throttle lever 28 is provided with a laterally extending arm 34 carrying a throttle stop screw 36, one end of said screw being adapted to engage in the well-known manner various lobes or steps of a fast idle cam 38 which is rotatably mounted on a stud 40. Behind the cam 38 is a lever 42 rotatably mounted 4 on the stud 40 and connected by a rod 44 with a choke valve lever 46 attached to the shaft l6.

If desired, a lost motion connection may be provided between lever 42 and lever 46. This connection as shown includes a slot 48 in the latter lever in which is received a laterally turned end portion 60 of rod 44, said end portion 50 being urged toward the upper end of slot 48 by a spring 52 coiled about the adjacent end of shaft l6 and attached to the end portion 50 of the rod 44 and to the lever 46.

Lever 42 has a laterally turned ear 54 which engages lug 56 on the fast idle cam 38 and limits movement thereof, said cam being so arranged that it is adapted to rotate clockwise by gravity when not engaged by the stop screw 36, said movement being limited, however, by car 54.

If desired, in order to prevent undue leaning of the mixture such as would cause the engine to stall during the initial starting period when the throttle is closed, means may be provided for limiting opening of the choke valve. This means includes a projection 58 on cam 38 Which is engageable by ear 54 of lever 42. The projection 58 is spaced from the cam a distance somewhat greater than the width of ear 54 thus permitting limited movement of the choke valve when the throttle is closed and the idle cam 38 is held against movement by frictional engagement of screw 36 with said cam. This arrangement is of importance primarily when the engine is being started cold. Thereafter, when the choke valve is partly open it is not required and is generally inoperative.

Means for limiting closing of the choke valve is shown as including a bell crank rotatable on the outer end of bearing 25 which projects from boss 26. The bell crank comprises a latching lever or pawl 62 normally depending from the bearing 25 and an arm 64 of less weight than lever or pawl 62 so that pawl 62 will be positioned by gravity as shown in Figures 1, 4 and 5. Arm 64 normally may extend at an inclination laterally of lever or pawl 62 and is adapted to be engaged by arm 34 of the throttle lever 28. The lower or free end of pawl 62 is turned laterally to provide a foot 63 which is adapted to engage a pin 66 fixed in cam 38, as described hereinafter, and a lug 68 on the bell crank is adapted to engage a pin I0 fixed in boss 26 for limiting clockwise rotation of said bell crank. When the pawl 62 engages pin 66 and limits counterclockwise rotation of cam 38 the closing of the choke valve is correspondingly limited by the one-way connection of ear 54 and lug 56 of said cam 38.

The cam 38 is also provided with a second pin 72 which is spaced from pin 66, pin 12 being adapted to be engaged by the wedge-shaped free end of a member 14, formed integral with the throttle lever 28, as will be fully described hereinafter. It should be borne in mind, however, that any other suitable arrangement of these parts may be used and that pawl 62 may be urged toward its depending or operative position, as shown in Figures 1, 4 and 5, by a spring or the like.

The operation of the device is as follows: AS- suming the engine to which the carburetor is attached has been operating at normal tempera ture but has been stopped, the positions of the various parts are as shown in Figure 5.

Upon cooling of the engine the thermostat 2B begins to close the choke valve l2 and is adapted to fully close same at normal atmospheric temperatures. However, the closing of said choke valve is interrupted by engagement of the stop screw 36 with the adjacent end of the intermediate step of the idle cam 38, the cam being urged counterclockwise, by ear 54 of lever 42 which engages lug 56 on said cam. The various parts then assume the positions shown in Figure 1. Should the throttle be opened only sufllciently so that the stop screw 36 is clear of said adjacent end of the intermediate step of the idle cam 36 choke valve l2 will be closed further by the thermostat but will still be retained in a part open position by engagement of pawl 62 with pin 66 on said cam. It should be noted that under these conditions the closing force of the thermostat, if the temperature is sufficiently low, will overcome the counter force of spring 52 so that the laterally turned end 50 of rod 44 is moved to the lower end of notch 48 of lever 46 by said force of the thermostat.

Preparatory to starting the engine when cold, it is necessary to actuate the accelerator pedal, or other throttle actuating mechanism, to partly open the throttle so that the stop screw 36 is moved away from the fast idle cam, and the arm 34 of the throttle lever engages arm 64 of the bell crank and raises said arm, thereby rotating the pawl 62 in a counterclockwise direction and out of the path of pin 66. It will be understood that in order to secure movement of the pawl 62 so that same is rotated out of the path of the pin 66 the throttle is opened a substantial amount such as to or beyond the position shown in said Figure 2. The thermostat then will close the choke valve and upon release of the accelerator pedal the spring 32 will effect closing of the throttle, the various parts of the device then being in the positions shown in Figure 3. It will be noted that pin 66 is in the path of pawl 62 and prevents said pawl from assuming its normal gravity position and that the stop screw 36 engages the highest step of the fast idle cam so that the throttle I4 is held open sufficiently to provide the required relatively large volume of fuel mixture to the cold engine during the cranking thereof. As the choke valve is closed by the thermostat during the cranking period the amount of air that can be drawn through the induction passage of the carburetor is restricted in the usual manner and the engine is supplied with the necessary extremely rich mixture.

Upon cranking of the engine there is a sudden rush of air into the carburetor due to the suction of the engine pistons. This sudden inrush of air tends to cause an excessive opening of the choke valve. However, by providing the ear 58 on the fast idle cam 38 the opening of the choke valve is limited to that desired for efiecting the proper proportions of air to fuel for starting by engagement of said ear 58 by the ear 54 of lever 42, it being understood that the stop screw 36 frictionally holds the cam 38 against movement.

As the engine begins to fire and run under its own power the suction of the pistons increases but said suction is insufiicient to effect additional opening of the choke valve, due to the engagement of the stop screw 36 with the cam 38, until the throttle is opened and the stop screw moved away from the cam. Normally the operator of the vehicle will thus open the throttle at this period of operation thereof to increase the speed of the engine and to perform the necessary operations to start the vehicle in motion. Immediately upon release of the cam 38 by stop screw 36 the choke valve is free to open farther than the limited starting position but the thermostat is so calibrated and arranged that it will not permit such opening of the choke valve as to allow the cam to rotate to a position whereat pin 66 is out of the path of pawl 62. However, the

position of the cam .is now such that the pin 12 is in the path of the wedge-shaped end of member 14 of the throttle lever 28 and will be engaged thereby as the throttle is moved toward closed position and upon closing of the throttle to a position other than that of the highest stop of the cam, said wedge-shaped end will positively effect clockwise rotation of the cam suiiicient to move pin 66 out of the path of the pawl 62 and permit the latter to assume its normal gravity position in the path of pin 66 as shown in Figure 4. The pawl is then in a position whereat it will positively limit counterclockwise movement of the cam and thereby positively hold the choke valve in a partly open position against the valve closing force of the thermostat. The proportion of air to fuel is thus increased to supply the required moderately or slightly rich mixture to the engine during the warming-up period.

Should it be desired to adjust the relationship between the member 14 and pin 12 the same may be efiected by suitably deforming member 74 although any other suitable means may be provided for making such adjustment.

It is generally desirable to have the member 14 move the cam 38 in a clockwise direction slightly beyond the position whereat pin 66 is clear of the pawl 62, thereby assuring sufiicient clearance between pin 66 and foot 63 to insure movement of the pawl to its gravity position. Thereafter, upon initial opening of the throttle, said opening of the throttle being less than the amount required to efiect rotation of the pawl '62, out of the path of the pin 66, member 14 moves away from pin 12, whereupon the cold thermostat moves the choke valve toward closed position until pin 66 is engaged by pawl 62 thereby preventing further closing of the choke valve and retaining said valve in the desired partly open position.

It has been found that under certain operating conditions of some engines the lost motion connection between rod 44 and lever 46 improves the operation of the engine during the initial portion of the warming-up period when the pawl 62 is operative to limit closing of the choke or air valve l2 and the engine temperature is so low that the normal latched position of said valve, as effected by the pawl, admits too much air to provide the desired richness of the mixture for the engine at such operating temperatures. Under said conditions use of the lost motion connection permits the ratio of air to fuel to be reduced by the cold thermostat which in cooperation with spring 52 adjusts the position of the choke valve relative to its normal latched position, the valve closing force of the cold thermostat being sufficient during the initial portion of the warming-up period to overcome the force of spring 52 and to partly close said choke valve relative to said latched position. The adjustment of the choke valve is limited by engagement of end 50 of rod 44 with the ends of slot 48, engagement of said end 56 with the lower end of the slot limiting closing movement of the choke valve by the thermostat and engagement of said end 5|] with the upper end of said slot 48 limiting opening movement of said valve by the spring 52. As the thermostat is warmed by the engine its valve closing force is gradually reduced. The spring 52 overcomes the diminishing valve closing force of said thermostat and efiects gradual opening of the choke valve until end 50 reaches the upper end of slot 48. Said choke valve is then in its normal latched position. It is to be understood that the lost motion connection is effective during the initial portion of the warming-up period while the pawl 62 is engaged with the pin .66 and the thermostatic temperature is low enough so that it will overcome the force of spring 52 whether the throttle is in the substantially closed or idling position, or in an open position whereat the stop screw 36 is out of engagement with the fast idle cam 38.

The pawl 62 is effective to limit closingof the choke valve throughout the throttle range which controls the lower speed range of the engine when suction conditions in the carburetor may, under certain well-known conditions, be so low as not to open the choke valve sufiiciently against the force of the cold thermostat. Above said lower speed range the suction of the engine is high enough to provide adequate opening of the choke valve and movement of the pawl 62 out of the path of pin 66 occurs without interfering with the operation of the engine.

It will be understood, therefore, that when extremely low suction conditions may occur in the carburetor during the initial portion'of the warming-up period of engine operation or until the choke valve has opened sufiiciently so that pin 66 will not engage pawl 62, said pawl when in its extreme depending position will prevent closing of the choke valve beyond a predetermined position and prevent diminution in the quantity of air being admitted to the carburetor, thereby maintaining the desired proportion of air to fuel during said warming-up period. However, as the engine warms up to normal operating temperature, the choke valve moves to the fully open position and cam 38 rotates by gravity, when not engaged by stop screw 36, to the normal idle position as shown in Figure so that stop screw 36 will rest on the lowest step of said cam when the throttle is closed. A normal mixture is then supplied to the engine.

If desired, the usual extension 80 of the throttle lever may be provided, said extension being adapted to engage stud 40 to limit opening movement of said throttle lever. The throttle lever 28 may also be provided with a part 82 for engagement with a lug 84 on the fast idle cam 38 when the throttle is moved to the wide open position, thereby effecting a partial opening of the choke valve to relieve a flooded condition of the carburetor such as may occur when said choke valve is closed by a cold thermostat.

While one embodiment of the invention has been illustrated and described it will be apparent to those skilled in the art that various changes may be made in the form, construction and arrangement of the parts withoutfldeparting from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

What is claimed is:

1. A control mechanism for carburetors having a pressure actuated air valve and a throttle valve, comprising a temperature responsive device for governing the degree of opening of the air valve, a pivoted lever, means providing a one-way connection between the lever and air valve, means for limiting movement of the lever whereby closing movement of the air valve is limited, the effectiveness of said means being unaffected by movement of the throttle within a lowe throttle range, and means efiective when the throttle is in a substantially closed position to limit opening of the air valve.

2. In control mechanisms for an internal combustion engine having a choke valve openable by suction in the carburetor, a throttle, a fast idle cam, and means including a lost motion connection connecting the cam with the choke valve, comprising an abutment on the fast idle cam, a latch engageable with said abutment whereby the choke valve is held in the partly open position, said latch becoming effective upon opening of the choke valve beyond a predetermined partly open position, means operable when the choke valve is partly open for positively opening said valve to a position whereat the latch becomes effective, said means being operated as the throttle approaches closed position, stop means connected with the throttle and engageable with the fast idle cam, means operable only when the stop means is in engagement with the cam for limiting opening movement of the choke valve, and means for releasing the latch upon opening of the throttle valve beyond a substantial predetermined partially open position.

3. Control mechanism for internal combustion engine carburetors having a choke valve openable by suction in the carburetor and a throttle, comprising a temperature responsive device adapted to control the opening of the choke valve, means adapted to latch the choke valve in a partly open position upon opening of the choke valve to a. predetermined partly open position, said means permitting additional opening movement of said choke valve, means associated with the throttle for releasing the latching means upon opening movement of the throttle beyond a substantial predetermined partly open position, said latch means being unaffected by throttle opening movement up to said predetermined partly open position, means fo positively opening the choke valve at least to the position whereat the latching means becomes effective, means adapted to limit the opening movement of the choke when the throttle is substantially closed, and means whereby limited adjustment of the position of the choke valve relative to its normal latched position may be efiected by the temperature responsive means.

ROBERT W. SUTTON. ALBERT H. WINKLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,262,408 Read Nov. 11, 1941 2,163,904 Winkler June 27, 1939 2,139,555 Coffey Dec. 6, 1938 2,124,778 Hunt July 26, 1938 2,160,410 Blattner May 30, 1939 2,160,411 Blattner et a1 May 30, 1939 2,166,899 Blattner July 18, 1939 2,218,699 Coffey Oct. 22, 1940 2,156,390 Henning May 2, 1939 

